New evidence has emerged about the alleged role of United Nations troops in causing a cholera epidemic in the Caribbean nation of Haiti.

A top US cholera specialist, Dr Daniele Lantagne, said after studying new scientific data that it is now "most likely" the source of the outbreak was a camp for recently-arrived UN soldiers from Nepal - a country where cholera is widespread.

Dr Lantagne was employed by the UN itself in 2011 as one of the world's pre-eminent experts on the disease.

The new evidence could have serious implications for the UN, which is facing an unprecedented legal and moral challenge in Haiti - as well as a multi-billion dollar compensation claim from victims' families.

More than 7,500 people have died from the cholera epidemic in Haiti since it started in late 2010. Hundreds of new cases are still being registered every week.

The most likely source of the introduction of cholera into Haiti was someone infected with the Nepal strain of cholera and associated with the United Nations Mirabalais campDr Daniele Lantagne, US cholera specialist

It is by far the largest cholera outbreak in the world in recent years - with more cases than on the whole of the African continent.

Prior to this outbreak, and despite Haiti's many other problems - including a devastating earthquake in January 2010 - the country had not recorded a single case of cholera for over a century.

Cholera is spread through infected faeces and once it enters the water supply it is difficult to stop - especially in a country like Haiti which has almost no effective sewage disposal systems.

After studying molecular data known as full genome sequencing on the strain of cholera found in Haiti - and that prevalent in Nepal in 2010 - Dr Lantagne said: "We now know that the strain of cholera in Haiti is an exact match for the strain of cholera in Nepal."

Mountain of claims

In 2011 Dr Lantagne was employed by the UN as one of a "Panel of Experts" tasked with looking into the outbreak.

The 2011 UN report - co-signed by her - acknowledged that inadequate toilets in the Nepalese UN camp in the mountain town of Mirabalais could have leaked the cholera bacterium into the nearby Meye River which flows into the country's main waterways.

But the report stressed that the outbreak "was not the fault" of any "group or individual".

The Panel of Experts added that the subsequent spread of the disease across Haiti was due to many factors - including the country's deeply inadequate water supply and almost non-existent sewage disposal systems.

Now, Dr Lantagne says the new genome data (in addition to other evidence) has changed her view since she had co-authored the UN report which effectively said no-one was to blame.

There were patients all over the floor. They were reaching out and grabbing my feetDr Rosana Edward, Hopital Saint Nicolas

"We can now say," Dr Lantagne said, "that the most likely source of the introduction of cholera into Haiti was someone infected with the Nepal strain of cholera and associated with the United Nations Mirabalais camp."

The UN's Head of Humanitarian Affairs in Haiti, Nigel Fisher, acknowledged the new information but said he could not comment on its substance.

"I know there's new information there," Mr Fisher said.

"But the investigation is still with the [UN's New York] legal office, so I'm not able to say anything at this time until that's gone through the due process."

Mr Fisher sought to stress, however, the work the UN was doing to mitigate the effects of the cholera.

"What I can tell you about is the work I'm co-ordinating to respond to that terrible epidemic and the fact that we've seen a significant decline in cases over the last year. If we take any encouragement, we take encouragement from that."

The UN's lawyers are facing a mass compensation claim being pursued by Haitian and US lawyers against the UN.

Dignified weeping

The victims' families have lodged an official claim at UN HQ in New York for $100,000 (£62,500) for those who died and $50,000 for those who fell sick. The total claim runs into many billions of dollars.

After spreading along rivers in late 2010 the number of cases exploded in the coastal town of Saint Marc - before moving on, with deadly speed, into the slums of the capital Port au Prince.

Dr Rosana Edward was the first doctor to encounter the disease in St Marc's main public hospital, the Hopital Saint Nicolas.

"I remember that day very well," Dr Rosana - as she is fondly known in the hospital - told me in a stiflingly hot ward.

There had been no cholera in Haiti for about 100 years until 2010

"My first cases had fever and diarrhoea. I looked at their stool samples and I said to myself 'Hey!,I think this is cholera!' - but I was also confused because we don't have cholera in Haiti.

"The next day the hospital was full to overflowing," Dr Rosana said.

"There were patients all over the floor. They were reaching out and grabbing my feet.

"'Help me'," they pleaded, "'Please, help me'."

I asked Dr Rosana if she had heard the reports that the UN was to blame for introducing cholera into Haiti.

"I've heard those reports," she replied, "but I don't know if they are true. I don't have the proof."

"Haiti doesn't need this cholera," the 40-year-old medic then said. "We have so many other problems."